Final answer:
The Milky Way is a spiral galaxy with dust, gas, and young stars; elliptical galaxies consist of older stars with a red color; and irregular galaxies have a disorganized shape. The phrase about arms extending from a core full of black holes suggests description 3 applies to spiral galaxies like the Milky Way.
Step-by-step explanation:
To match each galaxy to its description, we must consider the defining features of spiral, elliptical, and irregular galaxies.
A. The Milky Way - As a typical large spiral galaxy, it contains a central bulge, a disk, spiral arms, and both young and old stars. Interstellar material is spread throughout its disk, with new star formation occurring especially in the spiral arms, which are typically dusty and contain bright emission nebulae and hot, young stars.
B. Elliptical galaxy - These galaxies are spherical or ellipsoid in shape and consist almost entirely of old stars, demonstrating very little star formation activity. They exhibit no spiral arms and their light is dominated by older, reddish stars. While they contain very little interstellar matter, some elliptical galaxies do contain a small amount of it.
C. Irregular galaxy - These are galaxies with disorganized shapes that do not fit into the category of spiral or elliptical. They can have patches of star formation and contain young stars, dust, and gas.
Therefore, the correct matches are:
A. The Milky Way - 1. contains dust, gas, and young stars
B. Elliptical galaxy - 2. contains mostly older stars with a red color
Description 3, arms extend from a core full of black holes, does not align clearly with the given options. However, since spiral galaxies like the Milky Way have defined arms and a central core where a supermassive black hole may reside, it can be inferred that this description applies to A. The Milky Way.